1. Field of the Invention
The present invention generally relates to printing inks, and more particularly relates to heat activated or dye sublimation inks used with ink jet printers.
2. Description of the Prior Art
Dye sublimation inks are commonly used with ink jet printers to produce color images directly on a substrate or on a transfer medium from which the image is transferred to the substrate. In particular, there are two basic types of dye sublimation inks used for ink jet printing: water-based inks and oil-based inks. Furthermore, there are particular advantages and disadvantages to each of these types of inks.
Water-based dye sublimation inks provide excellent print density and are compatible with many printers. Printers using such water-based inks do not require venting, and there is very little odor given off, and any environmental hazards associated with the use of water-based inks are minimal. However, one of the primary disadvantages of using water-based inks is that it causes paper cockling when printing thereon, as the water is absorbed by the paper medium. Another disadvantage of water-based inks is that they will not work on grand format solvent printers.
Oil-based dye sublimation ink compositions were created to solve the problem of paper cockling prevalent with the use of water-based inks. An oil-based dye sublimation ink, or more generally, a hydro-carbon based ink, has the advantage over water-based dye sublimation inks of not cockling the paper medium on which it is printed. Furthermore, oil-based dye sublimation inks are compatible with most grand format printers, with some minor modifications to the printer components. One disadvantage, however, with such oil-based inks is that they exhibit a low print density.
There are used in the printing industry solvent-based pigment inks, which have characteristics that are substantially as good as those of water-based ink compositions and are well suited for use various mediums, as cockling of the paper is avoided. However, there are no solvent-based dye sublimation inks known by the inventors herein to be currently used in the printing industry. The reason for the believed non-existence of solvent-based dye sublimation inks is the difficulty of manufacturing such a dye sublimation ink composition that is suitable for use in the printing industry. The dye tends to only partially dissolve in the solvent, which lowers the density and “stability” of the composition. The term “stability” herein means maintaining the dye particles in solution and further maintaining the solution's physical characteristics, such as surface tension and viscosity, fairly constant.